Two component glass body for tape casting phosphor in glass led converters

ABSTRACT

The present invention is directed to a method for preparing a glass device comprising the steps of: —preparing a mixture comprising: —at least two glass components, —a solvent, —at least one binder system, —optionally at least one defoamer, —blending the mixture to form a blend mixture, —grinding the blend mixture to form a grinded mixture, —casting the grinded mixture to form a layer, and —drying the layer to form a dried layer of a glass device. The present invention is further directed to a glass device, a wavelength converter and a light emitting device comprising the glass device and/or the wavelength converter.

TECHNICAL FIELD

The invention relates to the field of solid-state lighting and morespecifically to glass devices for LED technology.

BACKGROUND

Phosphor in glass converter plates have been produced using Spark PlasmaSintering, wire sawing, polishing/lapping and dicing. Phosphor in glassconverter plates may also be produced using a traditional thermalsintering process followed by wire sawing, polishing/lapping and dicing.Attempts to produce items via a traditional tape cast, punch and sinterprocess have failed due to loss of shape and dimensions.

U.S. Publication No. 2004/0145308 discloses a light source having aluminescence conversion body. The luminescence conversion body is apolycrystalline ceramic body which is united with a solution of adopant.

U.S. Pat. No. 9,420,664 discloses a light emitting device having a lightemitting composite material including a glassy material and a pluralityof phosphor particles suspended within the glassy material.

U.S. Pat. No. 6,147,019 discloses a glass composition incorporated intoa castable dielectric composition for the fabrication of multilayercircuits.

Zhang et al, Laser Photonics Re. 2014, 8(1), 158-164 discloses aphosphor-in-glass color converter.

SUMMARY

It is an object of the present invention to obviate the disadvantages ofthe prior art.

It is another object of the present invention to provide a method forproducing a glass device that might be used in LED applications.

It is another object of the present invention to provide a glass devicethat might be used in LED applications.

It is a further object of the present invention to provide a wavelengthconverter.

Furthermore, it is an object of the present invention to provide a lightemitting device comprising at least one glass device and/or at least onewavelength converter.

In accordance with one object of the present invention there is provideda method for preparing a glass device comprising the steps of:—preparinga mixture comprising:—at least two glass components,—a solvent,—at leastone binder system,—optionally at least one defoamer,—blending themixture to form a blend mixture, grinding the blend mixture to form agrinded mixture,—casting the grinded mixture to form a layer, and—dryingthe layer to form a dried layer of a glass device.

In accordance with another object of the present invention there isprovided a glass device prepared by a method according to the presentinvention.

In accordance with another object of the present invention there isprovided a wavelength converter prepared by a method according to thepresent invention.

The invention is further directed to a glass device comprising:—a matrixconsisting of at least one glass component, and—at least one glassparticle intercalated in the matrix.

The invention is further directed to a wavelength convertercomprising:—a matrix consisting of at least one glass component and atleast one phosphor, and—at least one glass particle intercalated in thematrix.

In accordance with another object of the present invention there isprovided a light emitting device comprising:—a light source, and—atleast one glass device according to the present invention and/or atleast one wavelength converter according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below on the basis of theexamples and with reference to the associated figures. The figures arediagrammatic and do not represent illustrations that are true to scale.

FIG. 1 shows a schematic drawing of a wavelength converter 1 accordingto embodiments. The wavelength converter comprises a glass component 2and glass particles 3. The wavelength converter 1 further comprisesphosphor particles 4;

FIG. 2 is a SEM image of a cross-section of a sintered wavelengthconverter according to embodiments;

FIG. 3 shows a spectral output of an exemplary wavelength converteraccording to embodiments; and

FIG. 4 shows a method for preparing a glass device according toembodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

For a better understanding of the present invention, together with otherand further objects, advantages and capabilities thereof, reference ismade to the following disclosure and appended claims taken inconjunction with the above-described drawings.

References to the color of the phosphor, LED, or conversion materialrefer generally to its emission color unless otherwise specified. Thus,a blue LED emits a blue light, a yellow phosphor emits a yellow lightand so on.

Embodiments of the present invention are directed to a method forpreparing a glass device 10 as shows in FIG. 4. The method comprises thesteps of preparing a mixture 12 comprising at least two glasscomponents, a solvent, at least one binder system, and optionally atleast one defoamer, blending the mixture 14 to form a blend mixture,grinding the blended mixture 16 to form a grinded mixture, casting thegrinded mixture 18 to form a layer, and drying the layer 20 to form adried layer of a glass device.

In an embodiment, the glass device is used in an optoelectronic device,especially in a LED (light emitting device).

The glass components may be selected from any silicate known in the art.The glass components may be selected from a group of silicates.Preferably the at least two glass components are different, i.e., theyhave different physical and/or chemical properties. Physical propertiesare, e.g., softening points, optical properties, e.g., refractive index,transparency, scattering properties, reflection properties and thermalexpansion. Chemical properties are, e.g., the chemical composition andthe chemical durability, such as the resistance to acids, bases and theattack from humidity.

In an embodiment, the at least two glass components have differentsoftening points. In a preferred embodiment, one of the glass componentshas a high softening point and the other glass component has a lowsoftening point.

In a further embodiment, at least one of the two glass components has asoftening point of between about 900° C. and about 1000° C. and/or atleast one of the glass components has a softening point of between about700° C. and about 800° C. In a further embodiment one of the glasscomponents has a softening point of between about 1500° C. and about1600° C., and/or at least one of the glass components has a softeningpoint of between about 500° C. and about 800° C. In a furtherembodiment, one of the glass components has a softening point of betweenabout 500° C. and about 800° C., and/or at least one of the glasscomponents has a softening point of between about 275° C. and about 400°C. The glass components may be chosen in this way that in the method forpreparing a glass device, at least one of the glass components softensor deforms and at least one of the other glass components does notsoften or deform. The glass component which neither softens, nor deformsmay act as a filler material in the mixture. The glass component whichhas a lower softening point may function as an inorganic binder in themixture. The glass which has a higher softening point may act as atransparent filler and does not soften or deform to any appreciableamount during the processing, e.g., during a sintering step. The glasscomponent having the higher softening point may form a matrix. The glasscomponent having the lower softening point may intercalate into thematrix. The composition of the glass components can be chosen with anindex of refraction that will increase the amount of scattering in theprocessed glass device, e.g., in the sintered glass device, as requiredby the desired properties of the finished glass device and any devicewhich comprises the glass device, e.g., a LED comprising the glassdevice.

The glass components may be chosen to influence the properties of theglass device. For example, one of the glass components may be chosenwith an index of refraction that increases the amount of scattering inthe glass device.

The at least two glass components may be selected from the groupconsisting of aluminosilicates, borosilicates, soda lime silicates,crown glasses, flint glasses, high silica glasses and low softeningpoint solder glasses.

The mixture for preparing a glass device may comprise two glasscomponents. The mixture for preparing a glass device may comprise threeglass components. The mixture for preparing a glass device may comprisefour glass components, or more.

The at least two glass components may be added in an amount of about 35vol-% to about 90 vol-%, preferably in an amount of about 40 vol-% toabout 75 vol-% with respect to the total volume of inorganic solids ofthe mixture.

The glass component(s) having the lower softening point may be added inan amount of about 35 vol-% to about 50 vol-% with respect to the totalvolume of the inorganic solids of the mixture.

The glass component(s) having the higher softening point may be added inan amount to add up to about 65 vol-% respect to the total volume of theinorganic solids of the mixture.

The mixture for preparing a glass device further comprises a solvent.The solvent may be a pure solvent, or a mixture of solvents.

In an embodiment, the solvent may be a protic or an aprotic solvent. Thesolvent may be an organic solvent, e.g., a mixture of methylethyl ketoneand ethyl alcohol or a mixture of trichloroethylene and ethyl alcohol.In an embodiment, the solvent is water.

The solvent(s) may be added in an amount of about 20 vol-% to about 80vol-%, preferably in an amount of about 40 vol-% to about 70 vol-% withrespect to the total volume of the mixture.

The mixture for preparing a glass device further comprises at least onebinder system. A binder system according to the embodiments of thepresent invention is a system that enables or facilitates the binding ofthe components of the mixture for preparing a glass device. The bindersystem may be responsible for an adhesive binding of the components. Inan embodiment, the binder system comprises a binding agent and aplasticizer. Preferably, the binding agent and the plasticizer arecompatible with each other.

The binding agent may be an organic compound, e.g., an acrylate, acryliccompound, cellulose, polyvinyl alcohol, polyethylene polyvinyl butyral.The binding agent may be an acrylic compound.

The binding agent may be added in an amount of about 3 vol-% to about 25vol-%, preferably in an amount of about 5 vol-% to about 20 vol-%, withrespect to the total volume of the mixture.

A plasticizer is a material that increases the plasticity and decreasesthe viscosity of a mixture. The plasticizer may be an organic compound,e.g., an ester, glycol, a phthalate, or an amine. The plasticizer may betriethanolamine.

The plasticizer may be added in an amount of more than 0 vol-% to about20 vol-%, preferably in an amount of more than 0 vol-% to about 4 vol-%with respect to the total volume of the mixture.

In an embodiment, the binder system is an acrylic binder system.

The mixture for preparing a glass device may further comprises at leastone defoamer. A defoamer eliminates or reduces the foaming of themixture, which in general facilitates the processing of the mixture. Thereduction or elimination of the foaming might also reduce the number ofinclusions, e.g., gas or air inclusions, in the mixture and the productmade out of the mixture. The defoamer is especially present if thebinder system is an acrylic binder system.

The defoamer may be selected from the group consisting of glycol andcarboxylate.

The defoamer may be added in an amount of more than 0 vol-% to about 0.5vol %, preferably in an amount of more than 0 vol-% to about 0.2 vol-%with respect to the total volume of the mixture.

The mixture may further comprise at least one phosphor. A phosphor is amaterial that converts light of a certain first wavelength to light of acertain second wavelength. The phosphor may be a polycrystalline,monocrystalline, or amorphous material. The phosphor may be an inorganicmaterial.

First wavelengths according to embodiments of the present invention arewavelengths between 300 nm to 570 nm. In an embodiment the firstwavelengths are between 350 nm to 500 nm. In a further embodiment thefirst wavelengths are between 420 nm to 480 nm.

Means for producing light of a first wavelength are, e.g., InGaN or GaNchips, or solid state laser diodes.

Second wavelengths according to embodiments of the present invention arewavelengths between 350 nm to 800 nm. In an embodiment the secondwavelengths are between 380 nm to 750 nm. In a further embodiment thesecond wavelengths are between 400 nm to 700 nm. In another embodiment,light of the second wavelength is white light.

In an embodiment, the phosphor is selected from the group consisting ofan yttrium aluminum oxide garnet structure with rare earth activation.Examples of an yttrium aluminum oxide garnet structure with rare earthactivation are Y₃Al₅O₁₂:Ce, (GdY)₃Al₅O₁₂:Ce, Y₃(AlMg)₅O₁₂:Ce,Y₃(AlSi)₅O₁₂:Ce, and Lu₃Al₅O₁₂:Ce. The mixture may comprise onephosphor, or may comprise a mixture of phosphors, e.g., a mixture oftwo, three or more phosphors. The phosphor(s) may be chosen to match theindex of refraction of the glass components. The phosphor(s) may also bechosen to mismatch the index of refraction of the glass component(s).The phosphor(s) may preferably be chosen to improve the opticalproperties of the glass device.

The phosphor may be added in an amount of more than 0 vol-% to about 45vol-%, preferably in an amount of about 2 vol-% to about 20 vol % withrespect to the total volume of the inorganic solids of the mixture inthe form of a slurry, i.e., the mixture of the solvent, the binder, theplasticizer, the optional defoamer, the glass components and thephosphor. Glass devices comprising a phosphor may also be calledwavelength converters.

The amount of the glass component(s) and optionally of the phosphor maybe in a ratio that results in the desired transmission andabsorption/emission properties of the resulting device at the desiredfinal size of the glass device.

In an embodiment to maintain shape, the inert materials (i.e., thephosphor and the higher softening point glass components) in combinationmight constitute from about 50 vol-% to about 65 vol-% with respect tothe total volume of the inorganic solids of the mixture. Within theinert portion of the materials the amount of phosphor can be 0 vol-%,which would result in a clear glass plate with respect to the totalvolume of the inorganic solids of the mixture. The phosphor componentmay be from about 20 vol-% to about 70 vol-% of the inert (with respectto sintering only) components with respect to the total volume of theinorganic solids of the mixture. Therefore for the lower softening pointglass may be present in an amount of about 35 vol-% to about 50 vol-%with respect to the total volume of the inorganic solids of the mixtureand the phosphor may be present in the amount of from about 10 vol-% ofthe total to about 65 vol-% of the total with the higher softening pointglass making up the remainder (of the sintered converter plate).

According to embodiments of the present invention, the method forpreparing a glass device comprises the step of preparing a mixture,which may be accomplished by adding the components of the mixture to asuitable device. The suitable device may be chosen in this way tofacilitate the further method steps.

The method further comprises the step of blending the mixture to form ablend mixture. The blending might be performed with a mixer, or anyother suitable device. The blending step might be performed betweenabout 0.1 hours to about 0.5 hours, preferably between about 0.1 hoursto about 0.2 hours. In an embodiment, the blending step is incombination with the mixing step.

The method further comprises the step of grinding the blend mixture toform a grinded mixture. The grinding may be performed in a roller mill.The grinding may be also carried out in an attritor mill, a bead mill,or a high shear mixer. The grinding step in general shreds the mixtureto particles with a size of between about 0.1 μm to about 50 μm. Thegrinding step might be performed between about 1 hour to about 120hours, preferably between about 1 hour to about 72 hours.

The method further comprises the step of casting the grinded mixture toform a layer. The casting step might be carried out on a temporary orpermanent substrate. A permanent substrate is a substrate that remainswith the glass device and is permanently connected to the glass device.A temporary substrate is a substrate that is disconnected from the glassdevice at some point of the method for preparing a glass device.Suitable permanent substrates might be sapphire or glass. Suitabletemporary substrates might be Mylar (a PET film). In an alternativeembodiment, the casting step might be performed on a surface and theresulting layer does not in any way bind to the surface. The layer mayhave a size of between about 5 μm to about 250 μm. In an embodiment thelayer has a size of between about 15 μm to about 150 μm.

The step of casting the grinded mixture to form a layer may alsocomprise the casting of several layers, e.g., two, three, four or morelayers, on top of each other.

The method for preparing a glass device further comprises the step ofdrying the layer to form a dried layer of a glass device. The dryingstep might comprise the drying in air. The drying step might alsocomprise a sintering step. The sintering might be performed at a normalpressure. The sintering temperature is normally below the working pointof the glass with a higher softening point, and below the melting pointof the phosphor. In a preferred embodiment, the sintering temperature ischosen in this way, that at least one of the glass components softensand at least one of the glass components does not soften. Typical sintertemperatures are between about 200° C. to about 1200° C., preferablybetween about 250° C. to about 900° C. In an alternative embodiment, thedrying step might be performed at an elevated temperature, at which noneof the components of the mixture softens or melts. In an aspect of thisembodiment, the elevated temperature is chosen that the solventevaporates. Typical elevated temperatures are between about 25° C. toabout 100° C., preferably between about 30° C. to about 80° C. foraqueous systems. The drying temperatures for organic solvent systems areselected as a function of the vapor pressure and flammability of thesolvent.

In an embodiment, the thermal processing removes the tape casting binderand the defoamer (if present) and the lower softening point glassbecomes the glue which binds the phosphor and higher softening pointglass together during the sintering (or fusing).

In an embodiment, the method for preparing a glass device furthercomprises the step of assembling at least two dried layers together. Theassembling step may be carried out by laminating in a press. In anaspect of this embodiment, at least three dried layers may be assembledtogether. In an aspect of this embodiment, at least four dried layersmay be assembled together. In an aspect of this embodiment, at leastfive dried layers may be assembled together. In an aspect of thisembodiment, more than five dried layers may be assembled together.

In an embodiment, the method for preparing a glass device furthercomprises the step of punching the dried layer into at least one plate.The punching may be carried out by a pneumatic or motor driven presswith the appropriate size die and punch. In an aspect of thisembodiment, the dried layer is punched to near net shape. The punchingmay lead to a plate having a size of between about 0.2 mm to about 20 mmin length, preferably of between about 0.4 mm to about 5 mm in length.

In a further embodiment, the method for preparing a glass device furthercomprises the step of sintering the at least one plate. The sinteringmight be performed at a normal pressure or at increased pressure. Thesintering temperature is normally below the softening point of thehigher temperature glass and below the melting point of the phosphor. Ina preferred embodiment, the sintering temperature is chosen in this way,that at least one of the glass components softens and at least one ofthe glass components does not soften. Typical sinter temperatures arebetween about 200° C. to about 1200° C., preferably between about 250°C. to about 900° C. In an alternative embodiment, the drying step mightbe performed at an elevated temperature, at which none of the componentsof the mixture softens or melts. In an aspect of this embodiment, theelevated temperature is chosen that the solvent evaporates. Typicalelevated temperatures are between about 25° C. to about 100° C.,preferably between about 30° C. to about 80° C. for aqueous systems. Thedrying temperatures for organic solvent systems are selected as afunction of the vapor pressure and flammability of the solvent.

In an alternative embodiment, the sintering step may be performed withthe dried layer, or the assembled dried layers, prior to any optionalpunching step. The sintering step may correspond to the sintering asdescribed above.

The method for preparing a glass device allows a typical tape cast,punch and sinter process to be employed producing semi-transparent, nearnet shape glass devices, e.g., LED phosphor converter plates, withoutexpensive and slow wire sawing, grinding/lapping, and dicing operations.

The method for preparing a glass device according to embodiments of thepresent invention might comprise the step of removing the organiccomponents and fusing the glass components to make a solid device.

The present invention is further directed to a glass device prepared bya method as described herein.

The present invention is also directed to a wavelength converterprepared by a method as described herein. As mentioned herein, a glassdevice comprising a phosphor may be called wavelength converter.Therefore, a method for preparing a glass device as described herein,wherein the mixture comprises at least one phosphor, might lead to awavelength converter.

As used herein a wavelength converter is a solid mean that converts atleast part of the light of a certain first wavelength to light of acertain second wavelength. The conversion is carried out by a phosphor.

The present invention is also directed to a glass device comprising: amatrix consisting of at least one glass component, and at least oneglass particle intercalated in the matrix.

A matrix according to embodiments of the present invention is aconfiguration of a material that allows embedding a further material.The matrix may also be described as a host material for a furthermaterial, which is embedded in that host.

The matrix of the glass device according to embodiments of the presentinvention consists of at least one glass component, especially of theglass having the higher softening point as described herein. The glasscomponent is preferably chosen to provide a stable matrix for thefurther components of the glass device. The glass component(s) arepreferably chosen to provide a transparent glass device and scatteringof light passing through the glass device is preferably omitted. In anembodiment, the matrix of the glass device consists of the glass havingthe higher softening point, combined with the phosphor (if present) toreach a level of between about 40 and about 60 vol-% of the sinteredobject.

The glass device further comprises at least one glass particleintercalated in the matrix. The glass particle(s) are preferably chosento provide a transparent glass device and scattering of light passingthrough the glass device is preferably omitted.

In an embodiment, the glass component(s) of the matrix and glassparticle(s) that intercalate into the matrix have different physicaland/or chemical properties. In an aspect of this embodiment, the glasscomponent(s) of the matrix and glass particle(s) that intercalate intothe matrix have a different softening point. Preferably, the glasscomponent(s) of the matrix have a higher softening point than the glassparticle(s) that intercalate into the matrix. The glass component(s) ofthe matrix may have a softening point of between about 900° C. to about1000° C., of between about 1500° C. to about 1600° C., of between about500° C. to about 800° C. The glass particle(s) that intercalate into thematrix may have a softening point of between about 700° C. to about 800°C., of between about 500° C. to about 800° C., of between about 275° C.to about 400° C.

In an embodiment, the glass component(s) of the matrix may be selectedfrom the group consisting of aluminosilicates, borosilicates, soda limesilicates, crown glasses, flint glasses, high silica glasses and lowmelting point solder glasses.

In a further embodiment, the glass particle(s) that intercalates intothe matrix may be selected from the groups consisting ofaluminosilicates, borosilicates, soda lime silicates, crown glasses,flint glasses, high silica glasses and low melting point solder glasses.

The glass particle(s) may have a size of about 0.1 μm to about 50 μm,preferably of about 0.1 μm to about 20 μm.

The matrix of the glass device may consist of one glass component. In analternative embodiment, the matrix of the glass device consists of twoglass components. In an alternative embodiment, the matrix of the glassdevice consists of three glass components. In a further embodiment, thematrix of the glass device consists of more than three glass components.

There may be one type of glass particle intercalated into the matrix ofthe glass device. In an alternative embodiment, two types of glassparticles intercalate into the matrix of the glass device. In analternative embodiment, three types of glass particles intercalate intothe matrix of the glass device. In a further embodiment, more than threetypes of glass particles intercalate into the matrix of the glassdevice.

In a further embodiment, there are other components than the glassparticle(s) intercalated into the matrix. The other components may beselected from light emitting materials such as phosphors, highlyscattering materials, such as zinc oxide, titanium dioxide, etc.Transparent crystalline materials may replace the higher softening pointglass, for example, sapphire.

The present invention is also directed to a wavelength convertercomprising: a matrix consisting of at least one glass component and atleast one phosphor, and at least one glass particle intercalated in thematrix.

The glass component(s), the phosphor(s) as well as the glass particle(s)may be chosen as for the glass device described herein.

The matrix of the wavelength converter according to embodiments of thepresent invention consists of at least one glass component, especiallyof the glass having the higher softening point, and at least onephosphor. The glass component is preferably chosen to provide a stablematrix for the further components of the glass device. The glasscomponent(s) are preferably chosen to provide a transparent glass deviceand scattering of light passing through the glass device is preferablyomitted. In an embodiment, the matrix of the glass device consists ofthe glass having the higher softening point and the phosphor combined toreach a level of between about 40 and about 60 vol-% of the sinteredobject.

In an embodiment of the present invention, the glass component(s) of thematrix and the glass particle(s) have different softening points. Thesoftening points are preferably chosen in that way that during theprocessing, e.g., during a sintering step, the glass component(s) do notsoften, wherein the glass particle(s) soften.

In a further embodiment, the glass component(s) of the matrix have asoftening point of between about 900° C. and about 1000° C. and/or theglass particle(s) have a softening point of between about 700° C. andabout 800° C. In a further embodiment, the glass component(s) of thematrix have a softening point of between about 1500° C. and about 1600°C., and/or the glass particle(s) have a softening point of between about500° C. and about 800° C. In a further embodiment, the glasscomponent(s) of the matrix have a softening point of between about 500°C. and about 800° C., and/or the glass particle(s) have a softeningpoint of between about 275° C. and about 400° C.

The wavelength converter further comprises at least one phosphor. Thephosphor may be a polycrystalline, monocrystalline, or amorphousmaterial. The phosphor may be an inorganic material.

In an embodiment, at least one of the phosphors is selected from thegroup consisting of a rare earth activated yttrium aluminum oxide garnetstructure, as e.g., described herein. The mixture may comprise onephosphor, or may comprise a mixture of phosphors, e.g., a mixture oftwo, three or more phosphors.

The wavelength converter according to embodiments of the presentinvention preferably converts light of a specific first wavelength to aspecific second wavelength. The wavelength converter may convert thelight of the specific wavelength completely to the specific secondwavelength. Alternatively, the wavelength converter may convert thelight of the specific wavelength partially to the specific secondwavelength. Especially, in the latter case, the emitted lightcorresponds to white light.

Embodiments of the present invention are further directed to a lightemitting device comprising: a light source, and at least one glassdevice according to embodiments of the present invention and/or at leastone wavelength converter according to embodiments of the presentinvention.

The light source may be any emitter of light of a certain wavelength.Examples of light sources are light emitting diodes (LED), lasers, etc.

The glass devices may be used in general lighting applications,automotive lighting applications, medical lighting applications, etc.

The wavelength converters may be used in general lighting applications,automotive lighting applications, medical lighting applications, etc.

The light emitting devices may be used in general lighting applications,automotive lighting applications, medical lighting applications, etc.

With the methods according to embodiments of the present invention (tapecasting, punching and sintering) wavelength converters may be producedwhich reduce the cost to manufacture compared to traditional methods.

EXAMPLES

A 1 liter HDPE bottle was loaded with: 1100 g of milling media; 168.58 gwater; 40.71 g water soluble acrylic binder (35% solids); 1.40 gplasticizer; 0.37 g defoamer; 45.80 g GdYAG:Ce phosphor; 59.59 g glasswith a softening point of 825° C. and 89.51 g glass with a softeningpoint of 935° C. These materials were roller milled for a total of 84hours. The resulting slurry was cast on a commercial tape caster with ablade height of 300 μm. This resulted in dried tape of 45 μm thickness.Three layers of the 45 micron thickness tape were laminated and punchedto form a square 1.232 μm on a side. Punched squares of the twocomponent glass and phosphor tape were air fired at 820° C. for 17hours. The sintered plates were 1.046 mm on a side and 115 μm thick;sintered to a theoretical density of about 92%. The sides of thesintered platelet are straight and square with no indication ofdistortion or rounding of the edges from the sintering operation. Thetypical spectral output of the converter is color coordinates Cx=0.270,Cy=0.245 and the emittance=119 lumens per optical watt blue light. FIG.3 shows the spectral output in graphical form.

While there have been shown and described what are at present consideredto be preferred embodiments of the invention, it will be apparent tothose skilled in the art that various changes and modifications can bemade herein without departing from the scope of the invention as definedby the appended claims. The disclosure rather comprises any new featureas well as any combination of features, which in particular includes anycombination of features in the appended claims, even if the feature orcombination is not per se explicitly indicated in the claims or theexamples.

This patent application claims priority of U.S. patent application Ser.No. 16/269,396, the content of which is incorporated herein byreference.

1. A method for preparing a glass device, the method comprising:preparing a mixture comprising at least two glass components, a solventand at least one binder system; blending the mixture to form a blendedmixture; grinding the blended mixture to form a grinded mixture; castingthe grinded mixture to form a layer; and drying the layer to form adried layer of the glass device.
 2. The method according to claim 1,further comprising assembling at least two dried layers together.
 3. Themethod according to claim 1, further comprising punching the dried layerinto at least one plate.
 4. The method according to claim 3, furthercomprising sintering the at least one plate.
 5. The method according toclaim 1, wherein the mixture further comprises at least one phosphor. 6.(canceled)
 7. The method according to claim 1, wherein the mixturefurther comprises at least one phosphor comprising a rare earthactivated yttrium aluminum oxide garnet structure.
 8. The methodaccording to claim 1, wherein the solvent is water.
 9. The methodaccording to claim 1, wherein the binder system comprises a bindingagent and a plasticizer.
 10. The method according to claim 1, whereinthe at least two glass components have a different softening point. 11.The method according to claim 1, wherein at least one of the two glasscomponents has a softening point of between about 900° C. and about1000° C. inclusive and/or at least one of the two glass components has asoftening point of between about 700° C. and about 800° C. inclusive.12. The method according to claim 1, wherein the mixture furthercomprises at least one defoamer. 13.-20. (canceled)